1. Field of the Invention
The present invention relates to a deflection yoke and a cathode ray tube (CRT) device using the deflection yoke.
2. Description of the Related Art
In recent years, energy-conservation measures are being taken in various fields and industries to prevent environmental destruction. The filed of CRT devices is no exception, and various attempts have been made to reduce power requirements of CRTs.
One attempt to reduce power consumption is to change the shape of deflection yokes.
FIGS. 1A, 1B, 1C, and 1D show, as one example, a color CRT device 100 resulted from such an attempt. The CRT device 100 has a 4:3 aspect ratio, a deflection angle of 100°, and a diagonal size of 19 inches.
FIG. 1A is a schematic side view showing the color CRT device 100.
The color CRT device 100 is composed of a CRT 102 and a deflection yoke 104.
The CRT 102 includes a glass bulb 112 composed of: a glass panel 106 having a rectangular front face; a glass funnel 108; and a cylindrical glass neck 110 that are joined together in the stated order. Formed inside the panel 106 is a phosphor screen (not illustrated), and installed inside the neck 110 is an in-line type electron gun (not illustrated). The in-line type electron gun is composed of three electron guns respectively corresponding to B (blue), G (green), and R (red) arranged in a horizontal direction (X axis direction) in the stated order when seen from the side of the panel 106.
The deflection yoke 104 is mounted along the outer surface of the glass bulb 112 in a manner to cover the boundary between the neck 110 and the funnel 108. That is, the deflection yoke 104 is mounted on the glass bulb 112 to cover a particular part. At the particular part, the outer surface of the glass bulb 112 has such a shape that cross sections taken along lines perpendicular to the tube axis (Z axis) of the CRT gradually change from circular to substantially rectangular as the section lines shift closer from the neck 110 to the panel 106. In this specification, the ouster surface of the glass bulb where the deflection yoke is mounted is referred to as a “yoke-mounting part”.
In the color CRT device 100, the in-line type electron gun emits electron beams along the tube axis (Z axis) direction of the CRT 102. The electron beams are then deflected by the action of deflection magnetic field that is generated inside the deflection yoke 104 so as to accomplish scanning over the phosphor screen provided inside the panel 106.
FIGS. 1B, 1C, and 1D are sectional views showing the deflection yoke 104 taken along the lines K—K, L—L, and M—M in FIG. 1A, respectively. The distances from the front face of the panel to the section lines K—K, L—L, and M—M in the axial direction (Z axis direction) are 56.9 [mm], 31.9 [mm], and 21.9 [mm], respectively.
As shown in FIGS. 1B, 1C, and 1D, the cross sections of the deflection yoke 104, roughly speaking, change from circular to substantially rectangular as the section lines shift closer from the neck 110 to the panel 106, so that the deflection yoke 104 conforms to the outer shape of the yoke-mounting part of the glass bulb 112.
To be more specific, the deflection yoke 104 is composed of: a funnel-shaped plastic separator 114 having a part of which cross section is substantially rectangular conforming to the outer shape of the yoke-mounting part of the glass bulb 112; a horizontal deflection coil 116 deposed along the inner surface of the separator 114; a vertical deflection coil 118 disposed along the outer surface of the separator 114; and a ferrite core 120 disposed externally to the vertical deflection coil 118 and having a part of which cross section is substantially rectangular.
A conventionally common deflection yoke (not illustrated) is normally composed of a substantially conical separator, a horizontal deflection coil disposed along the inner surface of the separator, a vertical deflection coil disposed along the outer surface of the separator, and a substantially conical ferrite core disposed externally to the vertical deflection coil. Due to its shape, such a conventionally common deflection yoke inevitably has gaps of a considerable size formed between the horizontal deflection coil and the outer surface of the glass bulb.
Unlike such a conventionally common deflection yoke, the deflection yoke 104 has the above-described construction. With this construction, it is intended to position the horizontal deflection coil 116 as close as possible to the outer surface of the glass bulb 112, so that the horizontal deflection coil 116 is positioned as close as possible to the path area of electron beams. This arrangement improves deflection efficiency and consequently reduces power consumption. In addition, in the deflection yoke 104, the vertical deflection coil 118 is also positioned closer to the path area of electron beams than in a conventionally common deflection yoke. This arrangement also contributes to power consumption reduction. Yet, the horizontal deflection coil 116 consumes much greater power than vertical deflection coil 118 does. Thus, the advantageous effect of the deflection yoke 104 is achieved primary by the horizontal deflection coil 116 being arranged close to the glass bulb 112.
As described above, though improvement in the shapes of the separator 114 and other components, the deflection yoke 104 has achieved improved deflection efficiency and, as a consequence, lower power consumption.
It should be noted, however, that the color CRT devices 100 composed of the deflection yoke 104 involve a problem that the convergence performance fluctuates to a greater extent than CRT devices composed of such a conventionally common deflection yoke as above.